1. Field of the Invention
In a detergent composition each component thereof has a distinct function which manifests itself either in manufacture, packaging, storage or use by the consumer.
The majority of commercial household detergent compositions contain (1) a foam-producing, surface-tension lowering substance, commonly referred to as the surfactant or detergent, (2) a detergent builder, usually present in higher proportions than the detergent, to aid the detergent power of the composition, (3) sodium silicate which, in addition to providing buffering action in the higher proportions functions as a builder, and in the lower proportions is employed for its anti-corrosion properties, (4) perfume, (5) anti-redeposition agents, (6) optical brighteners, (7) optionally small amounts of bleaches, colorants, etc., and (8) a detergent filler, or diluent.
The term "detergent filler" as used herein and as applied to detergent compositions, refers to any compatible inert substance employed as a diluent in detergent composition to facilitate the adjustment of the proportions of the other components to desired levels.
It is well known in the detergent art that sodium sulfate has been virtually the only detergent filler, or diluent, employed in fabric washing detergent compositions since the introduction of synthetic detergents for use in this type of composition. Recently however the supply of sodium sulfate has become limited, and substitutes, either partial or complete, are being sought in order to maintain an adequate supply of detergent compositions on the market.
2. The Prior Art
Sodium sulfate has long been the traditional filler for detergent compositions, as exemplified by the disclosures in the text "Synthetic Detergents," Davidsohn and Milwidsky, 5th ed., 1972, page 38, Leonard Hall, London (incorporated herein by reference).
The use of calcium carbonate in a detergent composition is disclosed in Netherlands application No. 7,305,925, bearing Ser. No. 248,546 and a U.S. priority date of Apr. 28, 1972. Therein particulate calcium carbonate, among other substances, having a particle size of less than 20 microns is disclosed as a crystallization seed to hasten crystallization of insoluble salts formed by hard-water cations and builder components, e.g., sodium carbonate, thereby reducing the amount of hard-water cations available to form insoluble derivatives of the detergent component. On the other hand, calcium salts having appreciable water solubility, such as calcium sulfate or hydrates thereof, are not acceptable as detergent fillers because of the resultant increase in the hardness of the wash solution, thereby interfering with the detergency process.